Generally, various methods such as a filtering method using a filter (U.S. Pat. No. 6,780,332), a high/low temperature treatment method (U.S. Pat. No. 5,366,746; U.S. Pat. No. 6,086,936), an antibiotic treatment method (U.S. patent Ser. No. 10/415,219), a disinfectant method (U.S. Pat. No. 6,583,176) and a UV irradiation method (U.S. Pat. No. 7,396,459) have been widely used in the art for inactivating a microorganism (a bacteria or a virus) or preventing a subject from being infected therewith. Recently, it has been developed a method for sterilizing a microorganism by using superoxide (O2−)/hydroxyl radical (OH) generated from photoreaction of a photocatalyst such as titanium oxide (U.S. Pat. No. 6,387,844; U.S. Pat. No. 6,777,357). The photocatalyst accelerates a chemical reaction by absorbing light from the outside. Among the photocatalysts, titanium oxide is a stable substance, but under ultraviolet (UV) light, it loses electrons and holes are formed thereon, leading to the excitation into an unstable state. At this time, superoxide (O2−) or hydroxyl radical (OH) generated from the excitation exerts antibacterial activities by inducing the oxidization or degradation of microorganisms and viruses around. Due to such strong oxidizing power, the attempts for applying titanium oxide to the sterilization by coating the same onto the surface of a support or spreading it in underwater have been remarkably increased. Because said method of coating the support with titanium oxide or dispersing it in an aqueous solution does not have selectivity to a microorganism of interest, the most cases are to merely utilize radicals generated from titanium oxide itself. Further, there is no systemic research on the correlation between the number of microorganisms and the concentration of titanium oxide, and the consideration of UV strength and a period of time being irradiated. For example, in a water system, there are problems in that the residence time of radicals generated from titanium oxide is not last long, and its antibacterial activities is lowered when the distance between the microorganism of interest and the titanium oxide is not extremely close. U.S. patent application Ser. No. 12/743,340 discloses a method for immobilizing titanium oxide particles with a biomolecule, but it provides only the information on sensor application of the immobilized complex and not antibacterial activities thereof.
Sakai et al. reported that a microelectrode comprised of titanium oxide can be used in killing T24 human bladder cancer cells. They also reported that if the microelectrode comprised of titanium oxide is 10 cm or longer distant from the cells, there is no effect of killing the cells. In this research, such poor antibacterial activities are because that direct oxidation is not actively occurred on the surface of the cells due to a very short life span of radicals generated from titanium dioxide (Sakai et al., Chemistry Letter, 1995, 185). In case of using the titanium oxide particles having no selectivity, there is a possibility of sterilizing normal useful microorganisms as well as target microorganisms being sterilized. Further, as suggested in the previous research, because the radicals generated by UV irradiation cannot be delivered to the microorganism, there is a disadvantage in that its antibacterial activity is not strong. The study for utilizing titanium oxide as an antibacterial composition has been actively pursued and relating products have been manufactured. But, there is no report on the development of titanium oxide photocatalytic particles having selectivity to a microorganism of interest as disclosed in the present invention.